Electronic multiple comparator



M. sHlowlTz ETAL 'ileanov. 25. 1953 Jan. 28, 1958 are assigned to'each digit ofthe number.

United States Patenti() ELECTRONIC MULTIPLE CONIPARATOR MarcShiowitz vand Howard M. Robbins, LosAngeles,

Calif., assignors, .by mesne assignments, to Hughes AircraftfCompany, Acorporation of Delaware 'Application-November 25, 1953, Serial No. 394,439

.-8 Claims. (Cl. 340-149) `1This inventionrelates to an electronic multiple comparator; andI more particularly, to an electronic multiple comparator for comprising and indicating the relative magnitudes-cfm plurality of binary numbers represented -by-'aj'plura1ity of sets of binary coded electrical digit signals; respectively; byl comparing the relative magnitude of corresponding digit signals.

v'In' copending U. S; application for patent, Serial No. 394,441, for Electronic Magnitude Comparator, tiled November-25, 1953, -byRobert R. Johnson, there is disclosed a-system for-comparing and indicating the relative -magnitudesfofftwo=binary numbers. According to the basic conceptof the Johnson invention, the relative magnitudes=oftwo-weghted"binary numbers are directly indic'ated4 by the-sense of the nonidentity'of the most significant-nonidentieal corresponding digits of the two numbers. -The Johnson application discloses anumber -offsystems forf-makingfuse of this principle to carry out Ihecomparison of two'binary numbers.

' 'lhepresentinvention discloses further improvements inucomparatorsfbased upon the same basic concepts-as the-Johnson.'system-wherein, however, the comparison processesare extended to the simultaneous comparison of a plurality of Abinary numbers and the instantaneous .inc'lica'tion ofrrthe relative magnitudes of the numbers beingzcompared More-specifically, the present'invention: relates to .a-comparator for comparing a plurality of-weigh-ted.binary-numbers and instantaneously indicating .the-.largest or the smallest of the numbers as soon asfthe .relative magnitudes of the numbers have been established.

The icomparator of the present invention provides that' the 1 comparison process be carried out by comparing signalsirepresenting corresponding digits of the :numbersin the orderv of most significant digit signals iirst. Thecomparator includes one output channel for each.of.the numbers, beingv compared and, initially, an -output.,signal.is .provided on each output channel. As .each set of successive digit signals is applied to the comparator,,outputsignalsa removed from the channels corresponding to numbers larger or smaller than ,the remainingnumbers, according to the desired comparison. Accordingly, atthe. conclusion of the comparison operation output signals remain on the channel correspondingv to the. smallest or largest of the numbers. Where apluralty. ofthe numbers are identical, and smaller or larger. than'the. remaining numbers being compared, an outputLsignalis provided on each ofthe output chann'els corresponding to the identical numbers.

Th'e lcomparator of the present invention is directly applicable'to the comparison of binary numbers which mayi=be=arrangedin^order of relative magnitudes accord- .ing to-ta weightingscheme whereby values of magnitude In particular, the comparator-fis applicable to'the comparison. of multi- Ldi'git,-.binary numbers in which particular-digitsof the number :carrythe same-or greater weight than digits less Amongthe. moreT common binary Asystems-of p 2,821,696 Patented Jan. 28, 1958 -tion will ibewreferredfto'as #weighted binary numbers.

. Itfris;:thereforewanfobject ofthe present inventionato provide an electronic magnitude-.comparator for comparing. t and `.indicating theurelative .-magnitudes. of t a 'plu- -ralitygaof binaryeznumbers aepresentedsas a;.plurality-of sets of binary coded electrical digit signals, respectively, byu comparing ;=the relative magnitudes-'of Vcorresponding digit signals@ -Another..objectof [the present invention is =to :provide a.. systeme ifor :comparing-.-y and f .indicating the largest; .-or alternativelytthe .smallest lotta-pluralityfof vweighted binary vnumbersrepresentedfby-"a-Vplurality of :sets-.of binary coded-.electricalndigitasignalm respectively, by comparing .the relative magnitudest.of\ correspondingdgit signals.

- A vfurtherc object .ot-the .present 'inventionis to --provide an electronic. comparator. which. -sequentially compares corresponding digit signals of;a plurality -of -sets ofA binary oodedelectricaL- digitssignalsxl-representing a pluralityvof numbers, respectivelya. and. instantaneously indicatesthe .largest or.the smallestoftthenumbers.

..It.-is, yet.. another object-.tof the presentinventionfto provide.- an. electronic nmagnitude. comparator -for :comparingrand.A indicatingnthelargest'. or..-the smallestf of a plurality-of numbers .expressed-as.--setsf-of binary. coded ;acteristic of. .the invention, both as.to.1`ts organization ancLmethodtnf. .pperationy together` with.,fl.uther.:objects and. advantages thereof,. will.. be better-.aunderstoodirom `the following. description z consideredin. connection with the.. accompanying :drawing .in which. =one :embodiment .of the invention, is.,illustrated 4by,way r .of..exampl.. .It..is to .be expressly understood, however, that. the drawing is for the. purpose. of illustrationand-description only, and is not4 intended. as..a .denitionf lthelimits of.the invention.

Fig., 1 is,.a. block.. diagramaof .an..electronic..magnitude comparator accordingtozthe present invention;-.and.

Fig. 2 is a block diagram illustrating an alternative component-forme comparator-ofl-ig.. 1.

Referring slow,v to .the drawings, .there is. shown .in.-Fig. 1 an electronic, magnitudecomparator. according. to.,the present invention .which provides for .the comparisonaof a plurality of weightedabinary.. numbers and..the.indi cation of. `tlf1e.smallest.. of the..,numbers., As..shown..zin Fig. l, the .comparator ,includes .a plurality .of input signal sources 101,.102, 103.and:10n -forsupplyingmomplementary electrical.;signalf-sets/A, B,f, C, .C and N, representingr-the numbers `tot bel compared,4 respectively, .to a.gatingzmatriXf210 which in turn supplies input signalskto a.plurality:otfbistablel elements 21122125213 and 21n forvindicating the results N:of :the: comparison: operation. Each of..the ;bistab1e:elements also receives: input signals f rom..a yreset` signal'. source .410..1and-supp1ies' an output. signal to .gating. matrix. 210 which .also t receives clock or comparisonpulses from 4a clock pulsesource 310.

More specifically, the input signal .-sets supplied by sources 101,'102,',103'and 10n.represent".lirst, second, third andn'th numbers. to be comparediandinclude one signal for eachfdigitof'the number.represented,.tl1e signalsbeingsupplied' in the lorder of most.- signilicant digit signal rst, corresponding digit signalsat the.same time. The signals suppliedmay be bivalued voltagelevel signals, in which case a.l 'digit may be yrepresentedby a signal oflrelatively high voltage level, While a "0" 'digit l-nated the l stable state.

while the signals presented on output terminals B,

and represent the complements of the digits presented on the corresponding nonbar outputterminal. In other words, a digit signal is presented on a barred output terminal when a 1 digit signal is presented on the corresponding nonbarred output terminal and vice versa.

Input signal sets A, B, C and N are supplied to a plurality of logical and gates 311, 312, 313 and 31n, respectively, of gating matrix 210. The logical and gates, which may be similar to the diode logical and gates described in copending U. S. Patent application, Serial Number 305,955, for Electronic Gate, by Eldred C. Nelson, led August 23, 1952, are three-terminal logical and gates and receive in addition to their respective input signals from the corresponding input signal source, clock pulses from source 310 and control signals from a logical or" gate 515, which will be further defined in the discussion which follows. Each logical and` gatel is responsive to the application yof corresponding 1 signals from its corresponding input signal source and logical or gate 515 to pass a simultaneously applied clock pulse from source 310 to its output terminal.

The output terminals of logical and gates 311, 312, 313 and 31n are connected to the K input terminals of bistable elements 211, 212, 213 and 21n, respectively, the I input terminals of the bistable elements being connected to reset signal source 410. Bistable elements 211, 212, 213 and 2in, which may be conventional Eccles- Jordan multivibrators, are responsive to signals applied to their K input terminals to set to one of their stable states, which will be denominated the "Of stable state, and to signals applied to their J input terminals to set to the other of their stable states, which will be denomi- Each bistable element has an output terminal upon which a signal of comparatively high voltage level is produced when the bistable element is in its "1 state and of comparatively low voltage level when the element is in its 0 state. In accordance with the notation previously adopted, these signals will be referred to as 1 and O signals, respectively, here- Z logical and gate, which may be similar to the diode logical and" gates heretofore described, receives a com' plementary input signal from one of input signal sources '101, 102,V 103 and 1011 and is responsive to l signals applied to both of its inputrterminals to produce a 1" outputgsignal. The complementary signal applied to each logical and gate is that from the input signal source associated with the bistable element from which the and gates other input signal is derived. For example, and gate 511 receives the output signal from bistable element 211 and signal from source 101.

The output terminals of logical and" gates 511, 512, 513 and 51u, in turn, are connected to the input terminals of logical or gate 515. This gate may be similar to the logical diode or gates described in copending U. S. Patent application, Serial No. 327,133, for Diode, Pulse Gating Circuits, by Richard D. Forrest, filed December 20, 1952, now Patent No. 2,762,936, and is responsive to the application of a 1 input signal to any of its input terminals to produce a 1 output signal on its output terminal. As has been mentioned previ- 4 connected to one input terminal of each of logical and gates 311, 312, 313 and 31u.

The operation of the system thus described may be better understood by first considering the response of the system when used to compare and indicate the smaller of two weighted binary numbers. An embodiment of the invention for carrying out such a comparison operation need only include two input signal sources, two bistable elements and the logical gating circuits associated therewith. In the discussion which follows, it will be assumed that the embodiment includes only input signal sources 10l and 102, bistable elements 211, 212 and the logical gating and control circuits associated therewith.

Considering now the operation of the system thus described, prior to the initiation of the comparison operation, bistable elements 211 and 212 are set to their 1" stable states by means of reset signals applied to their J input terminals from reset signal source 410. To carry out the comparison operation, input signal sources 101 and 102 may apply the signals representing the two numbers to gating matrix 210 in the order of most significant digit signals first, corresponding signals being applied at the same time. Upon the application of each pair of input digit signals, clock pulse source 310 applies a clock pulse to each of gates 311 and 312.

If the input signals presented by inputvsignal sources 101 and 102 represent corresponding 0 digits, a 0 signal will be applied to each of gates 311 and 312 and the applied clock pulse will not be passed by either gate. lf the digit signals presented by input signal sources 101 and 102 represent corresponding l digits, "0 signals will be applied to each of logical gates 511 and 512 and accordingly, logical or gate 515 will produce a 0 output signal thus inhibiting the passing of a clock pulse by either gate 311 and 312. lt will thus be seen that so long as corresponding digit signals are supplied by input signal sources 101 and 102, neither gate 311 nor gate 312 will pass a clock pulse,.and, therefore, neither of bistable elements 211 or 212 will be changed from its original setting.

However, upon the .application of nonidentical digit signals from the input signal sources, the conditions required for the passing of a pulse by logical gate 311 or .312 will be satisiied and one of the bistable elements will Assume first that the digits are dissimilar in the sense that input signal source 101 pre- 5 sents signals representing a l digit while input signal- -source 102 presents signals representing a "0 digit. It

be set to its O state.

will be seen that the "0 signal appearing on the B terminal of source 102 inhibits the passing of pulses by gate' 312 while, at the same time, the "l" signal supplied from the terminal of signal source 102 to gate 512 produces a output signal at gate 512. Accordingly, gate 515` y produces a "1 output signal. The occurrence of a 1f output signal .at both inputs to logical gate 311 causes the gate to pass a clock pulse and, accordingly, bistable ele-L ment 211 is set to its 0 state.

Once bistable element 211 has been set to its "0 state, its setting will not thereafter be changed until reset signals are again applied to its J input terminal. In addition, the setting of bistable element 211 to its 0 state inhibits the further response of gate 511 and accordingly, gate 515 will gain produce a 1 output signal only if gate 512 produces a loutput signal, that is if input signal source 102 produces a "1 output signal on its output terminal. Since input signal source 102 can never produce a "1 out- -posite sense, that is, the signal presented by source 101 represents a digit while the signal fpresentedebyr source 102 represents a 1 digit, bistable element`f212 will he set to its 0 state, while bistableelement 211,1'emains in its "1" state, and the system is rendered nonresponsive. to the application of further input signals. Itwill thus-.be seen that once nonidentical signals are applied to-the system, the response of the system to the applicationof further digit signals is effectively inhibited.

The setting of bistable elements 211 and 212, once nonidentical corresponding digit signals are applied to the system, may be interpreted asa directindication of the relative magnitudes of the two numbers being compared. Thus, it will be seen that the bistable element corresponding to the input signal source which presents the 0 digit signal of the first occurring dissimilar pair of digits-remains in its 1 state throughout the comparison operation, while the bistable element corresponding to the input signal source which presents the "1 digit signal of the tirst occurring dissimilar pair of digits is set to-its 0" state by the comparison operation.

As heretofore pointed out in the discussion of the binary system of enumeration, and as more fully discussed in the aforementioned Johnson application, the sense of the nonidentity of the most significant dissimilar pair of corresponding digits of two weighted binary-numbers is a direct indication of the relative magnitudes of the two numbers. In other words, the -1" digit of the dissimilar pair occurs in the larger of the two numbers while the 0 digit of the dissimilar pairoccurs inthe smaller of the two numbers. Accordingly, the tinal setting of the bistable elements may be interpreted as -indicating the relative magnitudes of the two numbers, the 1 set bistable element indicating that the corresponding input signal has represented a smaller number than the "0 set bistable element. The smaller of the twonumbers being compared will thus be seen t be indicated by the appearance of a l or relatively high voltagelevel signal on the output terminal of the corresponding bistable element. As previously discussed, if both of the numbers being compared are identical, neither bistable element will be set to its 0" state and accordingly, both bistable elements will present 1" output signals.

The basic comparison system of the present invention may be enlarged to provide for the simultaneous comparison of a plurality of binary numbers by including additional input signal sources and bistable elements and associated gating circuits within the system. Such an embodiment, shown in Fig. 1, has been previously described.

Considering now the operation of the comparator of Fig. 1 in the light of the previous discussion, bistable elements 211, 212, 213 and 21n may be initially setto their 1 stable states by means of reset signals applied to their I input terminals from reset signal sourcel 410. To carry out the comparison operation, input signal sources 101, 102, 103 and 10n may apply the 'signals representing ynumbers A, B, C and N to gating matrix 210 -in the order of most significant digit signals tirst, corresponding digit signals being applied at the same time. Upon the application of each group of input digit signals, clock pulse source 310 applies a clock pulse to the logical and gates to which it is connected. The -system will be responsive to the applied input signals in a manner analogous to that of the two number comparator previously described.

Accordingly, the application of similar 1 or "0" digit signals from all of the input signal sources will produce no response within the system. However, upon the occurrence of a nonidentity between any two ormore input signals, the bistable elements corresponding toe-applied 1" input digit signals will be set to their "0" states while the bistable elements which receive "0 input signalswill remain in their 1 states. The setting ofl aparticular vbistable-element to its "0 state will render that element insensitive to the application of further input signals and alsocause the elementitorpfoduce a1ftlfonrelativelywlow voltage outputsignal.v ,The fan ,j;gate,whi chreceivesthe output Vof such.af,particularl bistable element will be inhibited and,` accordingly, the conditions underwhich or" gatel .515 produces a,"1'f output;si gnal will not-be further satised -by the inputsignals corresponding to the O set bistable element. 'Iheomparison process willcontinue with respect to the, numbers, corresponding ,to bistable elements .which have ,not.been set to their 0 state until all but one of the bistableelements; remains lfin its l state, or until -all of .theovdigitssignals-Of the numbersjbeing compared havebeenlappliedto the system- If during thecomparison tprovtesssgall ofthe bistable elemeutsexcept one haye,been setto ltheir "0" states, the .bistable element, rernainipgjmits state thereby indicates that the correspondingapplied input signals, represent the smallest :number: of the groupof numbers comvar ed. Itshould be. noted that` this condition mayexist before all of the signals representing the -numbers have been applied to the comparator and if desired,A the comparisonoperation may-berdiscontinued before all digit signals have been applied. If,`however, after all digit signalsvof the numbers llave, ,been,applied, more` than one of the'.v bistable elements remainsjn its 1 state, the bistable elements remainingtinthe 1 state thereby indicate that all oi the corresponding input signals have been identical and that thisfidttnticalinput` signal represents, `a number,smallerfthan.,the.,nurnbers,applied to any of-the 0" set bistable elements,

The,multipleomparatonshownfin Fig. 1 may -be utilized to compare-.andfindicatcfthe largest of a plurality of'numbers by interchangingythegAandA, B and B, C and ;,C, N lt\nd-l-I-ir'1puts, respectively. 'Considering now thegtrcsponseof the-systemmnderthis -mode of operation, all of the bistable elements may -be^initially set to their fl" state by the. application of areset signal from reset signalsource 410. To carry out the comparison operation, input signalsources 101,102, 103 and 10n may supply signals identical in. form to Ythose previously dis.- cussed. However, signals A,' B,' andv are now ,applied to gates 311, S12/313 and 31a, respectively, while signals A, B, C and N-are applied to gates 511, 512, 513 and 5in, respectively.

lt will be seen from the previous discussion that any particularv` bistable element will now be set to its 0" state when the input vsignal corresponding to that element represents a "0" digit, if at the same time, a 1" digit is represented by thev signals from any other input signal source. The setting of any particular bistableelement to its 0" state will thus indicate that the number corresponding to that lparticular bistable element is smaller than a number being applied to oneor more of the other input lends.

If, during the comparison process, all of the -bistable elements except one have been set to their 0" states, the bistable element remaining in its "1" state thereby indicates that the corresponding applied input signals have represented the largest number of the group 0f numbers compared. It should be noted that this condition may exist before all of the digit signals representing the numbers have been applied to thecomparator and as set forth above, the comparison operation may be discontinued beforeall digit signals have been applied. If, however, after all digit signals of the numbers have been applied, more than one of the bistable elements remains inits 1" state, the bistable elements remaining in their 1" state thereby indicate that all of the corresponding input signals have been identical and that this identical input signal represents a number larger than the numbers applied to any of the 0" set bistable elements.

While the comparator shown in Fig. 1 has been dis- -cussed with particular reference to what is'lcnown-as voltage level gating, it should be understood that .the system may beas readily implemented for pulsing-gating.

When it is desired to employ pulse techniques throughout the system the bistable elements shown in Fig. 1 may each be replaced by the logical structure shown in Fig. 2, which is similar to the dynamic iiip-op shown and discussed in an article entitled Dynamic circuit techniques used in SEAC and DYSEAC, by R. D. Elbourn and R. P. Witt at pages 2 through 9 of The Transactions of the I. R. E. Professional Group on Electronic Computers, for March 1953, volume EC-2, No. 1.

As shown in Fig. 2, the element includes a logical or gate 601, a logical inhibition gate 602 and a delay clement 603. One of the inputs to logical or gate 601 may be denominated the I input. The output terminal of the or gate is connected to the normal input terminal of inhibition gate 602, which has its output terminal returned to the remaining input terminal of or gate 601 through delay element 603. The inhibition input terminal of gate 602 may be denominated the K input terminal of the element.

Considering the response of the structure thus de-r scribed, a pulse applied to the I input terminal of logical or gate 601 will be passed to its output terminal and thence through the inhibition gate in the absence of a pulse simultaneously applied to the K input terminal of the inhibition gate. This pulse, in turn, will be delayed by delay element 603 and then be applied to the other input terminal of logical or gate 601. If it is assumed that the system is lossless, pulses will thereafter appear on the output terminal of gate 602 at intervals equal to the timed delay of delay element 603. However, the application of an appropriately timed pulse tothe K input terminal of gate 602 Will inhibit the passing of pulses by this gate and, accordingly, once a pulse is applied to 'the K input terminal, no further pulses will appear on the output terminal of gate 602. v

When used to replace the bistable element shown in Fig. 1, the signals formerly applied to the I and K input terminal of the respective bistable elements may be applied to the J and K input terminals of the structure shown in Fig. 2 and the output signal formerly taken from the 1 output terminal of the bistable element may be taken from the output terminal of inhibition gate 602. The delay of delay element 603 may be equal in time to the interval between the application of clock or comparison pulses from source 310. The reset signals supplied from reset signal source 410 may be identical to the clock or comparison pulse supplied from source 310 and may be supplied simultaneously with the application of the rst or most significant digit signals. The logical and and or gates may be similar. to the diode and and or gates heretofore described except that they may now be responsive to l and pulse input signals if desired.

The comparator thus described may be used to compare and indicate the relative magnitudes of a plurality of numbers in a manner similar to that discussed in connection with the embodiment shown in Fig. l. The reset signals applied from reset signal source 410 may be applied to the respective I input terminals of the elements simultaneously with the application of the first or most significant digit signals of the numbers. As long as the applied digit signals are identical, the clock pulses from source 410 will continue to appear on the output terminals of each of the elements at intervals of one pulse time. However, upon the application of nonidentical signals from any of the input sources, an inhibition pulse will be applied to the appropriate input terminal. The inhibition pulse thus applied will inhibit the passing of the circulating clock pulse and pulses will no longer appear on the output terminal of the inhibited bistable element. The final indication of the system will be identical to that of the previous embodiment except thaty the final output'signals will now be clock pulse signals rather than Voltage level signals.

vWl1 ile"a lossless system has been assumed for this embodiment of the invention, Yit should Abe understood that to achieve such a system in practice may require that additional amplifiers and pulse restoring circuits be inserted at various points within the system. Such circuits are well known to the art and are therefore, not considered to represent a departure from the scope of the present invention.

What is claimed as new is:

1. A system for comparing and indicating the relative magnitudes of a plurality of binary numbers expressed as a corresponding plurality of bivalued electrical signal sets, respectively, each signal set including at least one digit signal for each digit of the number represented, said system comprising: a plurality of bistable elements, one element for each signal set; first means coupled to said bistable elements for setting all of said bistable elements to a predetermined one of their stable states; second means coupled to said bistable elements and responsive to corresponding digit signals of said signal sets to change the setting of each one of said bistable elements to the other of its stable states when the digit signal associated with said one bistable element is dissimilar in one sense from another corresponding digit signal; and third means coupled to said second means for rendering said second means responsive to digit signals associated with a bistable element whose setting has not been changed and nonresponsive to digit signals associated with a bistable element whose setting has already been changed.

2. In a system for comparing and indicating the relative magnitudes of vfirst and second'binary numbers expressed as first and second bivalued electrical signal sets, respectively, each signal set including a pair of complementary digit signals for each digit of the number rep-y resented, the combination comprising: first and second bistable elements, each element producing an output signal when set to a predetermined oneof its stable states; means for setting said bistable elements to said one stable state; first and second logical and circuits yelectrically connected to said first and second bistable elements, respectively, each of said logical and circuits having first and Segond input terminals and an output terminal and being responsiveto signals applied to said first and second input terminals for producing an output signal on said output terminal to set the associated bistable element to the other of its stable states; means for applying one signal of each pair of complementary digit signals of said iirst and second sets to the first input termi nal of said first and second and circuits, respectively; a logical gating matrix for applying a signal to the second input terminal of each of said and circuits, said gating matrix including an output terminal connected to the; second input terminal of each of said an circuits, ai two-terminal logical or circuit, and rst and secondi two-terminal logical and circuits, each'having an out-i put terminal connected to an input terminal of said or circuit; means for applying the output signal of said first and second bistable elements to one input terminal of said first and second two-terminal logical and circuits, respectively; and means for applying the other signal ofi each of said pairs of complementary digit signals of saidf first and second sets to the other input terminal of said first and second two-terminal and circuits, respectively.

3. In a system for comparing and indicating the relative magnitudes of a plurality of binary members expressed as a plurality of bivalued electrical signal sets, respec tively, each signal set including a pair of complementary digit signals for each digit of the number represented, theI combination comprising: a plurality of bistable elements,I one for each signal set, each element producing an output signal when set to a predetermined one of its stable states; means for setting said bistable elements to said one stable state; a corresponding plurality of logical and circuits electrically connected to said plurality of bistable elements, respectively, ea-ch of said logical and circuits hav;

,ing first and` second input terminals and an output termina' and being responsive to signals applied to said first and second input terminals for producing an output signal on said output terminal to set the associated bistable element to the other of its stable states; means for applying one signal of each pair of complementary digit signals of Said plurality of sets to the first input terminal of said plurality of logical and circuits, respectively; a logical `gating matrix for applying a signal to the second input terminal of each of said and circuits, said matrix including a logical or circuit having a plurality of input terminals and an output terminal connected to the second input terminal of each of said and" circuits, and a plurality of two-terminal logical and circuits, one for each of said bistable elements and its associated signal set, eachr twoterminal and circuit having an output terminal connected to an input terminal of said or circuit; means for applying the output signal of each of said bistable elements to one input terminal of the associated two-terminal logical and circuit; and means for applying the other signal of each of said pairs of complementary digit signals of each signal set to the other input terminal of the associated two-terminal and circuit.

4. A system for comparing and indicating the relative i magnitudes of a plurality of binary numbers expressed as a corresponding plurality of bivalued electrical signal 10 of pairs of complementary bivalued electrical signal sets A, A, B, E, C, C N, representing in bilevel voltage form first, second, third nth numbers to be compared, respectively, each signal set including at least one signal for each digit of the number represented; first, second, third and nth bistable elements, one for each pair of signal sets, each bistable element producing an output signal when set to a predetermined one of its stable states; irst means for setting said bistable elements to said one stable state; second means responsive to a control signal and to signal sets E, C and N, respectively, to set the corresponding first, second, third and nth bistable elements to the other of their stable states; and a logical gating matrix for producing said control signal in response to application of each of signal sets A, B, C and N and the output signal produced by the corresponding bistable sets, respectively, each signal set including a pair of complementary digit signals for each digit'of the number represented, said system comprising: a plurality of bistable elements, one for each signal set, each element pro ducing an output signal when set to a predetermined one of its stable states; rst means for setting said bistable elements to said one stable state; second means responsive to simultaneous application of a control signal and one f signal of each pair of complementary digit signals of each of said plurality of sets to set the corresponding bistable element to the otherof its stable states; and means for producing said control signal, said means'includng a logical gating matrix responsive to simultaneous application of the output signal of each bistable element and the other signal of each of said pairs of complementary digit signals of the corresponding signal set.

5. A system for comparing and indicating the smallest of a plurality of binary numbers, said system comprising: a plurality of input signal sources for supplying a plurality of pairs of complementary bivalued electrical signal sets A, B, C, N, representing in bilevel voltage form first, second, third nth numbers to be compared, respectively, each signal set including at least one signal for each digit of the number represented; first, second, third and nth bistable elements, one for each pair of signal sets, each bistable element producing an output signal when set to a predetermined one of its stable states; tirst means for setting said bistable elements to said one stable state; second means responsive to a control signal and to signal sets A, B, C and N, respectively, to set the corresponding rst, second, third and nth bistable elements to the other of their stable states; and a logical gating matrix for producing said control signal in response to application of each of signal sets B, C and N and the output signal produced by the corresponding bistable element.

6. A system for comparing and indicating the largest of a plurality of binary numbers, said system comprising: a plurality of input signal sources for supplying a plurality element.

7. A comparator for comparing signals representative of a plurality of binary numbers and indicating the relative magnitudes of the numbers, said number-representing signals being supplied from a plurality of signal sources including one source for each number to be compared, said comparator comprising: a plurality of bistable elements, one for each signal source, each element producing an output signal when set to a predetermined one of its stable states; rst means for setting said bistable elements to said one stable state; a plurality of logical gating circuits, including one circuit for each of said bistable elements, responsive to the simultaneous application of a control signal and a number-representing signal representative of one binary digit from a signal source to set the corresponding bistable element to the other of its stable states; and means for producing said control signal, said means including a logical gating matrix responsive to the simultaneous application of the output signal from one of said bistable elements and a number-representing signal representative of another binary digit from the corresponding signal source to produce vsaid control signal.

8. In a comparator for comparing signals representative of a plurality of binary numbers and indicating the relative magnitudes of the numbers, said number-representing signals being supplied from a plurality of signal sources including one source for each number to be compared, the combination comprising: a plurality of bistable elements, one for each signalA source, each element producing an output signal when set to -a predetermined one of its stable states; first means for setting said bistable elements vto said one stable state; second means selectively responsive to a number-representing signal representative of one binary digit from a signal source to set the corresponding bistable element to the other of its stable states; and third means responsive to the output signal from a bistable element and a number-representing signal representative of another binary digit from the corresponding signal source to render said second means selectively responsive to said one -binary digit-representing signal.

References Cited in the le of this patent UNITED STATES PATENTS 2,590,950 Eckert et al Apr. 1, 1952 2,609,143 Stibitz Sept. 2, 1952 2,646,501 Eckert et al. July 21, 1953 

